The uptake of bovine serum albumin by the skin of bath-immunised rainbow troutOncorhynchus mykiss

In order to clarify the main site responsible for soluble antigen uptake in bath immunisation, the localisation of labelled bovine serum albumin (BSA) was examined in rainbow trout after bath administrations by hyperosmotic infiltration (HI) and direct immersion (DI). Quantitative analyses indicated that the main site of BSA uptake is the skin with a lesser role for the gills in both HI and DI treatments. These data were further confirmed by histological analysis. BSA was observed primarily in the intercellular spaces of the skin and gills after HI, while it was most common in epithelia of the skin and in macrophage-like cells in the gills after DI. Following either treatment, BSA was trapped by the secondary circulatory system in the skin and gills, as well as the kidney and spleen.